Underwater Mechanically Tough, Elastic, Superhydrophilic Cellulose Nanofiber-Based Aerogels for Water-in-Oil Emulsion Separation and Solar Steam Generation
Zhu Wu, Hongrui Sun, Zhiguang Xu, Huanjie Chi, Xiaomin Li, Shanchi Wang, Tao Zhang, Yan Zhao
Abstract
Cellulose nanofiber (CNF)-based aerogels are promising for various applications, but their poor water resistance and low underwater mechanical toughness hinder their applications. Here, we report the fabrication of covalent-cross-linked, CNF-based anisotropic aerogels through silane condensation and subsequent freeze-drying. The resulting aerogels show lamellar structures along the axial direction, enhanced hydrophilicity, excellent water resistance (soaked in water for 12 months without breakdown), and outstanding underwater mechanical toughness (without damage after 500 compression–release cycles). Also, the aerogels show an unusual underoil superhydrophilicity, which allows the aerogels to separate surfactant-stabilized water-in-oil emulsions through absorption with a high separation efficiency of 99.6%. Meanwhile, the excellent anti-oil-fouling ability endowed the aerogels with high recycle stability and reusability. Taking advantage of powerful antigravity water transportation (transfer rate of 3.75 mm/s at a height of 2.5 cm) imposed by the enhanced hydrophilicity and the interconnected radial-aligned channels, the aerogels were applied as structural components of the solar vapor generator, which showed a relatively high evaporation rate of 1.83 kg m–2 h–1 and water evaporation efficiency of 95.9% under one solar irradiation.